The invention relates to solar collector devices, and more particularly to mirrors or reflectors for such devices.
The efficient and economical generation of electrical energy from solar radiation has been one of the prime objectives of the energy industry in recent years. Both direct photovoltaic generation methods and indirect solar thermal methods have been used.
Solar thermal plants use one or more a reflecting surfaces to concentrate solar radiation onto a central receiver through which a working fluid, such as water, is circulated. The fluid is vaporized and the resulting fluid expansion is used to drive a turbine generator. The ideal reflecting surface for a solar thermal system is a parabolic mirror having the central receiver at its focal point. The mirror is also preferably movable in order to follow the sun across the sky. However, the production of such a movable, unitary mirror structure is very expensive, and due to mechanical support requirements such mirrors are limited in size.
As a compromise two primary alternative approaches have been used. The first uses multiple flat mirrors to direct the solar energy onto a central receiver. The mirrors are individually controlled so that they will concentrate the sun's radiation onto the collector throughout the day. The second approach uses an elongated trough having a parabolic cross-section to reflect the solar energy onto a collector which runs the length of the trough at the focus of the parabola. The trough is rotated along its longitudinal axis to follow the sun as it moves across the sky.
Both the multiple mirror and the parabolic trough are inherently less efficient than a single parabolic mirror. The multiple mirrors do provide a complete reflective surface and the flat mirrors collectively provide only a rough approximation of the ideal parabolic shape. The further difficulty and expense of controlling a large array of separate mirrors is also apparent. The parabolic trough suffers the inefficiency of being parabolic only in one dimension and thus does not provide optimum concentration of solar energy throughout the day.
It is therefore an object of the present invention to provide a solar collector mirror that is easy to install, maintain, and replace.
It is another object of the present invention to provide a solar collector mirror that is relatively inexpensive.
It is a further object of the present invention to provide a solar collector mirror whose shape and focal point can easily be altered.
It is yet another object of the present invention to provide a solar collector mirror which can be constructed in much larger sizes than present mirrors.
It is still another object of the present invention to provide a large solar collector mirror whose shape closely approximates the ideal reflector shape.